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Sheep’s Asian beginnings

24 April 2009

Sheep on a hill

A genetic study involving the University has suggested that sheep bred primarily for their wool and milk rather than their meat first arose in south west Asia before spreading to Europe.

Archaeological evidence has shown the domestication of sheep for their meat occurred around 11,000 years ago in south west Asia, before spreading to Europe, but up until now it was not known where later domestic animals bred specifically for secondary products such as wool first took place.

The team, including Professor Mike Bruford of the School of Biosciences found this specialisation of breeding also occurred first in south west Asia before spreading to Europe through a second migration. Their findings are published in the journal Science.

In coming to their conclusions, scientists examined endogenous retroviruses within the DNA of 1,362 sheep from 133 different breeds of domestic sheep and their closest wild relatives. The viruses are like genetic fossils - caught by sheep thousands of years ago whose DNA has been absorbed into the genetic code of the animal and passed on to every subsequent generation.

The sheep were tested for the presence of six independently inherited retroviruses and the team compared the prevalence of the different viruses amongst the sample group to ascertain when the viruses had first infected the sheep. By doing this they were able to identify the older species which pre-dated the more recently domesticated animals.

Professor Bruford said: "The new and groundbreaking aspect of this work is that it uses viral insertions of DNA into the genome to look at the order of events when sheep were domesticated and came to Europe. We can show that there were two episodes of migration because different viral insertions 'mark' different points in time. The first episode gave rise to most of the primitive breeds we have today and the second episode gave rise to most of the breeds we now use commercially. Previous approaches using DNA did not have this feature, meaning we were not able to distinguish events that in reality only occurred a few thousand years apart. This adds substantial new complexity to our understanding of animal domestication."

The team say that the tests used in the research can be applied to other species and be used to preserve specific breeds of animals.

The study was led by the University of Glasgow, and also involved academics from, amongst others, Texas A&M University and the University of Bradford. Their full findings are published in the paper ‘Revealing the history of sheep domestication using retrovirus integrations’.

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